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AASCIT Journal of Materials 2015; 1(2): 42-50 Published online July 20, 2015 (http://www.aascit.org/journal/materials) Radiation Degradation and Stability of Polymer Wangtong He, Xuejia Ding Beijing Laboratory of Biomedical Materials, Beijing University of Chemical Technology, Beijing, China Email address [email protected] (Xuejia Ding) Citation Wangtong He, Xuejia Ding. Radiation Degradation and Stability of Polymer. AASCIT Journal of Materials. Vol. 1, No. 2, 2015, pp. 42-50. Keywords Abstract Radiation Resistant Polymer In recent years, because of the advantage of radiation technology-low energy, clean, Materials, environmental protection, etc., so that the use of radiation technology for polymer Plasticizer, synthesis or processing research continues to heat up; however polymer materials Stabilizers, irradiated via high-energy radiation prone to produce free group or to react with atomic Antioxidants, oxygen in the air, resulting in the material cracking, crosslinking, branch, etc., it affects the Ligh Stabilizers, performance of the materials. In this paper, we focus on the need for the research of Hindered Amine Light Stabilizer radiation resistance of polymer material, It highlights the basic mechanism of polymer materials irradiation discoloration and the formulation of radiation resistant materials, which includes plasticizers, stabilizers, antioxidants and light stabilizers, the most representative is the study of a hindered amine light stabilizer and the latest irradiated Received: June 16, 2015 materials research. Revised: June 24, 2015 Accepted: June 25, 2015 1. Introduction It is well-known that the century of polymer materials paly a huge role. As polymer materials are widely used in medical and space technology, the development of research on radiation resistance of common polymer materials and space high-energy radiation and radiation resistance of high performance polymer materials gradually give rise to the attention of the countries all over the world. However, the vast majority of polymeric materials will change color-yellow, brown or black after undergoing high energy ray irradiation. In its radiation curing and radiation crosslinking process, due to the existence of radiation-induced discoloration affected its in processing performance (such as irradiation disinfection and sterilization) in many applications. Whereas radiation-induced changes in mechanical properties (and the chemistry which underlies these changes) have been extensively studied during the past four decades, radiation-induced changes in optical absorption have received little attention until quite recently and consequently this area has not been well explored. [1] Until recently, people realize the question for a more comprehensive and systematic exploration and research on the problem. 2. The Mechanism of Irradiation Discoloration The radiation degradation of polymer is the fracture of the main chain 、the lower molecular weight under the action of ionizing radiation, which turns out the solubility of polymer increase in the solvent, the corresponding the thermal stability and mechnical performance decrease. Because of the series of results producing by radiation degradation, so for the study of radiation degradation is far less attention than radiation crosslinking. In the process of polymer radiation degradation, the Oxidative degradation reaction will occur. 43 Wangtong He and Xuejia Ding: Radiation Degradation and Stability of Polymer 2.1. Radiation Degradation of Oxidation antioxidants of inhibition radiation oxidative degradation 、all Reaction kinds of light stabilizer and so on. Polymer irradiation discoloration whose products mainly 2.2. The Methods Irradiation Resistant include water, CO and CO 2 gas, alcohol, ketone, carboxylic acid and peroxide is the result of a series of reactions. For most We have already understood the mechanism of irradiation of the polymer, It is thought to be caused by radiation energy discoloration, based on the mechanism of it, we have a lot of automatic oxidation process, the process is as follows: research methods to prevent the color change of the polymer Initiation Reaction of Chain: materials.There is no doubt that the problem of the study will be very difficult, but I think that the study of this problem will RH→RH·→R·+H· have great significance. It will be further deepen for antioxidant, heat stabilizer and light stabilizers research. R·+O →ROO· 2 Radiation-resistant polymer materials will better applied to Propagation Reaction of Chain: humans. ROOH→RO·+HO· 3. The Basic Formula of Polymer ROOH→R·+HOO· Materials HO·+RH→R·+H O 2 3.1. Plasticizer ROO·+RH→ROOH+R· There is a large number of polar groups in the polymer RO·+RH→ROH+R· molecular and the intermolecular forces is strong. Not only making polymer processing performance deteriorate, but also Termination Reaction: causing polymer materials products stiffen, lacking of R·+R·→R-R elasticity and suppleness, which reflectes in physical and mechanical properties. There is some changes between the ROO·+R·→ROOR interaction force and the role of the intermolecular hydrogen bond force in polymer-plasticizer system after adding into a ROO·+ROO·→ROOR+O 2 certain amount of plasticizer. It makes polymer materials be easily processed and significantly increase of the elasticity and ROO·+RO·→ROR+O 2 flexibility in the products. That is to say, plasticizer is a Polymer materials fracture produce R· after high energy ray substance that adds into the material (usually plastic, resin or irradiation intermolecular; R· can react with oxygen to elastomer) to improve their processability 、flexibility and generate ROO· in the air; ROO· can also capture the hydrogen stretchability. Plasticizer can reduce system melt viscosity and atoms in polymer that produce ROOH and R·. From the above glass transition temperature and product elastic modulus, and chemical reaction equations, we can perceive that the will not change the basic chemical properties of the plasticized formation of R· is the direct cause of polymer materials materials. Polymer materials commonly used plasticizer is radiation photodegradation, Once produced alkyl oxygen free phthalate octyl lipid (DOP). Because of poisonousness of the radicals ROO·, it will take the hydrogen atoms of polymer DOP, there is some restrictions on the use of many countries. molecular chain to form the hydroperoxides. At room The current main non-toxic plasticizer have citric acid esters, temperature, hydrogen peroxide can be broken down slowly 1, 2-disubstituted cyclohexane dicarboxylic acid diisopropyl again to generate new free radical. there is no doubt that this ester type, Estman168 plasticizers, polyester plasticizer, will lead to further degradation of polymer materials. It is degradable biomaterials with plasticizer, epoxy plasticizer, simultaneity that chain rupture and crosslinking in the process etc. of polymer radiation degradation of oxidation. Chain fracture Citrate esters plasticizers are more easily moving out than make polymer relative molecular weight reduce while phthalate esters. It can be used in food packaging, medical brittleness reticular molecule generate by crosslinking, it leads appliances, children's toys and personal hygiene items, etc. 1, to the decreased of physical properties of the material. As a 2-disubstituted cyclohexane dicarboxylic acid diisopropyl result of the formation of the attraction of the conjugate group ester transparent and precipitate harderly, it has good and the fall of free radicals or ion make the polymer show the compatibility with polyvinyl chloride (PVC), so it can be used color change. Such as the macroscopic expression of for the preparation of transparent PVC. Eastman168 Polypropylene materials is yellow after high energy ray plasticizer which developed by the United States is a kind of irradiation. On this basis, we can improve the performance of environment-friendly plasticizers, it is characterized by the irradiation discoloration by enhancing the light stability of the security of higher and not cause harmful to human body. material performance: strengthen the shielding and absorption Polyester plasticizer is one main type of polymeric plasticizer, of radiation ray; reinforce the free radicals decomposition of it has the feature of the relatively high molecular weight and hydrogen peroxide; quench excited state molecules; capture can not easily move out, it can be used in high temperature free radicals. In other words, we can add plasticizer 、 AASCIT Journal of Materials 2015; 1(2): 42-50 44 insulation materials. Biodegradable plasticizer uses in materials like PVC by adding suitable amount of stabilizers, biodegradable materials, such as polylactic acid (PLA), it can which eliminates the materials that all had catalytic activity reduce itself hardness. Epoxy plasticizer is compounds for the thermal degradation reaction of chain (hydrogen containing three of epoxy group, it is the widely application of chloride and conjugated polyene).There are some kinds of plasticizer. More representative of the plasticizers is epoxy lead salt, metal soap, organic stannum, rare earth and soybean oil, which has good compatibility with PVC, the compound stabilizer we used commonly. advantage of it is high temperature resistant, and can not easily The type of lead salt stabilizer mainly refers to the basicity moved out, it also can make the active chlorine atoms of PVC of lead the inorganic and organic acids, such as three basicity chain more stability, and absorbe quickly
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